DJI F550 addon set

Here is a set of addons for DJI FlameWheel F550. It consist of following parts:

* 3rd floor board to mount flight controller above battery. GPS/Magnetometer and companion computer may be attached there also.
* Bottom mount to attach Tarot FY680 landing gears. Because overall size of mount is too large for my 3D printer I split it on two parts they are different a bit due to asymmetrical cutouts of F550 bottom board.
* Bottom mount back part is to isolate some modules from bottom board (which is power distribution board) and to fasten bottom mount parts with plastic zip ties and bolts.